The Microchemistry and Proteomics Core Facility (MPCF) supports laboratory and clinical research programs at MSKCC by 1) providing synthetic peptides and by 2) carrying out mass spectrometric and amino acid sequence analyses of proteins and peptides, generally for the purpose of identification, relative quantitative analysis and post-translational modification (PTM) analysis. Synthetic molecules are made according to specifications provided by the investigator. Polypeptides submitted for identification (either single proteins or mixtures), PTM analysis, quantitation or N-terminal sequencing are prepared by the lab requesting service. Information on chemistries and instrumentation, and expert advice on experimental approaches are provided by Core staff. The goal of proteomics is to analyze changing levels, local concentrations and post-translational modifications of proteins in cells, as well as to analyze higher-order networks of protein-protein interactions. Proteins and protein modifications are critical in the complex signaling pathways and regulatory processes underlying cell growth, division, differentiation, DNA repair, development, senescence, and in responses to bioactive agents, genetic alterations and disease. Dissection of multi-component protein complexes is therefore increasingly the focus of studies on molecular control mechanisms. Identification of unique components provides a powerful approach to the selective retrieval and identification of the companions. The impact that these services have provided, in facilitating research projects and enabling the timely progression of high priority research, can be recognized throughout the reports of the several research programs. In a multi-institutional study led by MSKCC, affinity-based proteomics was used to examine the cancer-specific networks that are coordinated by Hsp90. These studies showed that the HSP90 inhibitor PU0H71, developed by Dr. Chiosis (ET), preferentially targets tumor enriched Hsp90 complexes and can be used to affinity capture Hsp90-dependent oncogenic client proteins. The Core has supported the research of 46 investigators during the past year. Over the past grant period, investigators from 9 programs were supported and the Core has contributed to 168 publications.